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Morphology and behavior
The spiny dogfish has dorsal spines, no anal fin, and white spots along its back. The caudal fin has asymmetrical lobes, forming a heterocercal tail. The species name acanthias refers to the shark’s two spines. These are used defensively. If captured, the shark can arch its back to pierce its captor. Glands at the base of the spines secrete a mild poison.
Males mature at around 11 years of age, growing to 80100 cm (2.63.3 ft) in length; females mature in 1821 years and are slightly larger than males, reaching 98.5159 cm (3.235.22 ft). Both sexes are greyish brown in color and are countershaded. Males are identified by a pair of pelvic fins modified as sperm-transfer organs, or “claspers”. The male inserts one clasper into the female cloaca during copulation.
Reproduction is aplacental viviparous, which was before called ovoviviparity. Fertilization is internal. The male inserts one clasper into the female oviduct orifice and injects sperm along a groove on the clasper’s dorsal section. Immediately following fertilization, the eggs are surrounded by thin shells called “candles” with one candle usually surrounding several eggs. Mating takes place in the winter months with gestation lasting 2224 months (the longest of any vertebrate). Litters range between 2 and 11 but average 6 or 7.
Spiny dogfish are fished for food in Europe, the United States, Canada, New Zealand and Chile. The meat is primarily consumed in England, France, the Benelux countries and Germany. The fins and tails are processed into fin needles and are used in less expensive versions of shark fin soup in Chinese cuisine. In England this and other dogfish are sold in fish and chip shops as “rock salmon” or “huss”, in France it is sold as “small salmon” (saumonette) and in Belgium and Germany it is sold as “sea eel” (zeepaling and Seeaal, respectively). It is also used as fertilizer, liver oil, and pet food, and, because of its availability and manageable size, as a popular vertebrate dissection specimen, in both high schools and universities.
Conservation Status & Management
Once the most abundant shark species in the world, populations of Squalus acanthias have declined significantly. They are classified in the IUCN Red List of threatened species as Vulnerable globally and Critically Endangered in the Northeast Atlantic, meaning stocks around Europe have decreased by at least 95%. This is a direct result of overfishing to supply northern Europe’s taste for Rock Salmon, Saumonette or Zeepaling. Despite these alarming figures, very few management or conservation measures are in place for Squalus acanthias. In EU waters, a Total Allowable Catch (TAC) has been in place since 1999, but until 2007 it only applied to ICES Areas IIa and IV. It was also set well above the actual weight of fish being caught until 2005, rendering it meaningless. Currently (2009), the TAC stands at 316t for ICES Areas IIa & IV, 104t for ICES Area IIIa and 1,002t for ICES Areas I, V – VIII, XII & XIV. In addition, a maximum landing size of 100 cm has been imposed in order to protect the most valuable mature females. The European Commission has stated that the TAC for 2010 will be set at 0t, ending targeted fishing for the species in EU waters. It remains to be seen if populations will be able to recover.
In the recent past the European market for spiny dogfish has increased dramatically, which led to the overfishing and decline of the species. This drastic increase led to the creation and implementation of many fishery management policies placing restrictions on the fishing of spiny dogfish. However, since the species is a late maturing fish, it takes a while to rebuild the population.
In 2010, Greenpeace International has added the spiny dogfish to its seafood red list. “The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries.”
List of sharks
^ Kindersley, Dorling (2001,2005). Animal. New York City: DK Publishing. ISBN 0-7894-7764-5.
^ Fordham, S; Fowler, S.L; Coelho, R; Goldman, K.J; Francis, M; 2006. Squalus acanthias. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. www.iucnredlist.org
^ Greenpeace International Seafood Red list
Fordham et al. (2006). Squalus acanthias. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes a lengthy justification of why this species is vulnerable
Squalus acanthias (TSN 160617). Integrated Taxonomic Information System. Retrieved on 24 January 2006.
Froese, Rainer, and Daniel Pauly, eds. (2005). “Squalus acanthias” in FishBase. 10 2005 version.
Wikimedia Commons has media related to: Squalus acanthias
Spiny dogfish attacked by North Pacific Giant Octopus
Spiny dogfish at Animal Diversity Web
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Extant shark species
Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Chondrichthyes Subclass Elasmobranchii
Frilled shark (C. anguineus) Southern African frilled shark (C. africana)
Sharpnose sevengill shark (H. perlo)
Bluntnose sixgill shark (H. griseus) Bigeyed sixgill shark (H. nakamurai)
Broadnose sevengill shark (N. cepedianus)
Needle dogfish (C. acus) Dwarf gulper shark (C. atromarginatus) Gulper shark (C. granulosus) Dumb gulper shark (C. harrissoni) Blackfin gulper shark (C. isodon) Lowfin gulper shark (C. lusitanicus) Smallfin gulper shark (C. moluccensis) Taiwan gulper shark (C. niaukang) Leafscale gulper shark (C. squamosus) Mosaic gulper shark (C. tessellatus) Little gulper shark (C. uyato)
Birdbeak dogfish (D. calcea) Rough longnose dogfish (D. hystricosa) Arrowhead dogfish (D. profundorum) Longsnout dogfish (D. quadrispinosum)
Taillight shark (E. zantedeschia)
Longnose pygmy shark (H. marleyi)
Pocket shark (M. parini)
Kitefin shark (D. licha)
Cookiecutter shark (I. brasiliensis) South China cookiecutter shark (I. labialis) Largetooth cookiecutter shark (I. plutodus)
Pygmy shark (E. bispinatus)
Smalleye pygmy shark (S. aliae) Spined pygmy shark (S. laticaudus)
Bramble shark (E. brucus) Prickly shark (E. cookei)
Hooktooth dogfish (A. nigra)
Highfin dogfish (C. excelsum) Black dogfish (C. fabricii) Granular dogfish (C. granulatum) Bareskin dogfish (C. kamoharai) Combtooth dogfish (C. nigrum) Ornate dogfish (C. ornatum) Whitefin dogfish (C. ritteri)
New Zealand lanternshark (E. baxteri) Blurred lanternshark (E. bigelowi) Shorttail lanternshark (E. brachyurus) Lined lanternshark (E. bullisi) E.